Aim In case of mucinous adenocarcinoma (MA), cytologic atypia is usually mild to moderate, or may be absent in some cases, incurring a diagnostic pitfall in recognising MA in small tissue biopsy and cytology specimens. The purpose of this study was to evaluate the diagnostic accuracy of transthoracic fine needle aspiration (FNA) or core needle biopsy (CNB) for making a diagnosis of pulmonary MA.

Methods We retrospectively reviewed a consecutive series of 185 patients who underwent curative operation for MA. Among those patients, 105 patients underwent preoperative percutaneous FNA (n=34) or CNB (n=79). Eight patients underwent FNA and CNB for the same tumour. Diagnostic accuracies of FNA and CNB for making a diagnosis of MA were evaluated, and the contribution of various clinicopathologic parameters to subtyping accuracy was analysed.

Results Diagnostic accuracies of FNA and CNB in determining malignancy were 67.6% and 87.3%, respectively, and those for making a diagnosis of MA were 20.6% and 59.5%, respectively. Univariate analysis indicated that the type of biopsy procedure and prominent growth pattern of MA are significant factors for successful histologic diagnosis. Tumour nature on CT and the length of biopsy specimen were not related to successful diagnosis of histology subtyping of MA.

Conclusions CNB appears to be feasible and accurate for diagnosing a MA. Prominent growth patterns of MA are significant factors for successful histologic diagnosis of MA.